Cold-formed steelIntroductionFormerly the use of cold-formed thin-walledsteel sections was mainly confined toproducts where weight saving was of primeimportance, e.g. in the aircraft, railway andmotor industries. Simple types of cold-formedprofiles (mainly similar to hot-rolled shapes),as well as profiled sheeting, have also beenused as non-structural elements in buildingfor about one hundred years.Lecture Notes By: Prof. Dr. Nabil El-Atrouzy

Cold-formed steelIntroduction

continued

Systematic research work, carried out over the past

four decades, as well as improved manufacturingtechnology, protection against corrosion, increasedmaterial strength and the availability of codes ofpractice for design, have led to wider use of coldformed sections within the building industry. Inmany countries cold-formed steel construction isthe fastest growing branch of the structural steelmarket.

Lecture Notes By: Prof. Dr. Nabil El-Atrouzy

More Typical Products and Uses

Lecture Notes By: Prof. Dr. Nabil El-Atrouzy

Historical ReviewThe research for utilizing stainless steel in building structureswas due to the advancement of cold-formed steel, especiallyin the USA, by G. Winter and his followers, which resulted in adesign manual "Design of Cold Formed Stainless SteelStructural Members -Proposed Allowable Stress DesignSpecification with Commentary". On the other hand, researchon structural stainless steel for building use dates back only tothe late 1980's growth of economy, when the researchers andengineers intended to use stainless steel in heavy steelconstructions. This led to the Establishment of specification ofdesign and construction of heavy stainless steel structures.

Lecture Notes By: Prof. Dr. Nabil El-Atrouzy

Advantages

The use of cold-formed structural

members offers many advantagesover construction using morestandard steel elements:the shape of the section can beoptimized to make the best use ofthe material.there is much scope for innovation(in practice this has proved to bevery significant).cold-formed members combined withsheeting offer economic and reliablesolutions which provide a spacecovering function and lateral restraintagainst buckling. Light-weightindustrial buildings constructed formcold-formed members and sheetingare an example of the combination ofthese two effects (Figure 4).Lecture Notes By: Prof. Dr. Nabil El-Atrouzy

Linear Method for Computing Properties

of Formed SectionsIf the thickness of the formed section is uniform, thecomputation of properties of such sections can besimplified by using a linear or midline method. In thismethod the material of the section is considered to beconcentrated along the centerline or midline of the steelsheet and the area elements are replaced by straight orcurved line elements. The thickness dimension t isintroduced after the linear computations have beencompleted. Thus the total area A = L t and the momentof inertia of the section I = I t, where L is the totallength of all line elements and I is the moment of inertiaof the centerline of the steel sheet. The properties oftypical line elements are shown in Fig. below:

6. Linear Ix , moment of inertia of midlines of steel sheets:

Flanges: 2(1.208)(2.948)2 = 21.00Corners: 2(0.377)(2.861)2 = 6.17Web: 1/12 (5.416)3 = 13.24Total: 40.41 in.37. Actual Ix:Ix = Ix t = 40.41(0.105) = 4.24 in.48. Section modulus:Sx =Ix/(d/2) =4.24/3.0 = 1.41 in.3The accuracy of the linear method for computing theproperties of a given section depends on the thickness ofthe steel sheet to be used and the configuration of thesection. For the thicknesses of steel sheets generally used incold-formed steel construction, the error in the moment ofinertia determined by the linear method is usually negligible.The expected errors is less than 1% if the material is 1/4 in.or thinner.